Problem Reading Mifare cards on PN532 Customized board.

[anmol_workmails]

Antenna‌ pn532‌ NXP 

I have customized my own PN532 board.

1. For first assembly the board was working some time and some time it did not.(was getting i2c address , card read some time and other time it did not read the i2c address).without ground tap in antenna 

2. Second time same board i assembled i am able to read i2c every time. but it is not able to read any card.

      i tried nfc energy harvesting ic so without ground tap on antenna it showed no power, led glowed very less. then i ground tapped antenna so i was able to get full glow on LED on board energy harvesting ic. but still not able to read cards.

attaching the Schematic and board image

[IvanRuiz]

Hello,

Please help us to provide more information on below questions:

1. May I ask what is the purpose of the yellow wire in front of the antenna?

2. Is this connected to a ground plane in the antenna on an inner layer?

3. Why are the inductors different, or is this a typo?

Best regards,

Ivan.

[anmol_workmails]

Hii Ivan 

1. The yellow wire is used to connect antenna ground tap to board ground that is VSS.

2. Its a double side PTH board no inner layer.

3. Its a typo value 560nh both.( i have corrected in schematic after attaching the files)

Also i wanted to ask they are TVSS1 AND TVSS2 transmitter ground on chip different from other ground(VSS). should i use them for antenna ground tapping while not shorting it to VSS (keeping them separate)

[IvanRuiz]

Hello,

Please remove the ground from the antenna, only the matching circuit is ok to ground it. Please measure the antenna parameters with a Network analyzer e.g. a MiniVNA and match it correctly to the front-end so that it is correctly tuned at 13,56 MHz. Also please refer to the antenna design guide available in the following link: https://www.nxp.com/docs/en/application-note/AN1445_An1444.zip 

Best regards,

Ivan.

[anmol_workmails]

Hii Ivan

1. The yellow wire is used to connect antenna ground tap to board ground

that is VSS.

2. Its a double side PTH board no inner layer.

3. Its a typo value 560nh both.( i have corrected in schematic after

attaching the files)

Also i wanted to ask they are TVSS1 AND TVSS2 transmitter ground on chip

different from other ground(VSS). should i use them for antenna ground

tapping while not shorting it to VSS (keeping them separate)

Thanks

Anmol Kohli

BTech-2016 Electronics Engineer

Embedded Design Engineer

m:+91-9958811944 e: anmol.workmails@gmail.com